I have no idea, I never really tested it. But I heard that 9, 10, 11, and 12 are best for finding diamonds.
I usually do this Go to Y:11 Mine a 2x1 area for about 10-45 blocks. Turn to my right. Go down to Y:10 Mine a 2x1 area for 15-30 blocks Repeat until super breaker is refreshed. Once super breaker is refreshed I tear the hell out of everything around me
Mine a 2x1 hallway at level 11 for about 50 blocks then after go back to start of hallway and mine the top block of every side every 2 blocks as far as you can reach.
Um I never said anything about exp, I don't care about exp for money I use exp on books etc. I earn my money from what I mine.
mine at level 15. diamonds every thing spawns in yet there are no lava pits. best mining level. if you have a fire resistance potion or pyro + i would recommend mining at level 11. ConferateBoys